Curtiss Jenny Restoration

Welcome! We hope you enjoy following the restoration process of a 1918 Curtiss JN4D Jenny. Once completed, the aeroplane will be flown and displayed at the Candler Field Museum in Williamson GA (30 miles south of Atlanta). You can contact me below by clicking on "VIEW MY PROFILE"

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Location: Peachtree City, Georgia, United States

Saturday, December 06, 2008

Tail Post Tube

In my opinion, the hardest piece on a Jenny to make is the tube that holds the tailskid in place. It's a 1 inch tube of .058 thickness bent past 90 degrees (106 degrees to be exact) across a 1 in. radius (tight).

I decided to try and bent the tube with my three-die bender and a 1in. die. At .058, the tube was too thick to bend cold so heat was needed. My neighbor Nick Ballay came over to lend some muscle (see picture below) and we heated the tube with the torch.

The tube would bend all right, but when we tried getting the 1 in. radius, the tube would kink. After three pieces of tubing, we gave up. There had to be a better way.

I called Paul Dougherty. He made his Jenny skid tube on a vice. No Dies. No hydraulic bender. Fellow Bucker restorer Robert Johnston stopped by and I asked him for advice. Robert owned a machine shop for many years and he agreed with Paul's advice. He also told me a few tips (which you will read about later).

So, I borrowed some of my kids play sand and filled the tube. This prevents the tube from kinking easily. Just pack the sand into the tube and tape both ends.

Put the tube in the vice and start heating with the torch. Robert gave good advice here. He said you should heat the inner and outer radius of the curve. The hot metal will stretch (outside) and shrink (inside) while hot. He also said not to put the torch on the top and bottom. This is where the tube will kink and heating it will weaken the wall and actually make it kink easier.

Also, take your time. If you heat one tight spot and bend there, it will kink. I heated one area, bent a little, then heated next to it, bent a little, then heated the other side of the first bend and finally worked over the entire area. Sure enough, the tube began to move.

Heat the outside and the inside (not the side)

Another thing I learned - get the outside hot (red, but not melting) then heat the inside and start pulling. Not too much. You can feel it move. Slowly is good. Then go back to the outside (while the inside is hot) and pull again. You can see the amount of area I heated in the pictures.
This method worked perfectly! I got the 106 degree bend with little trouble. I guess the entire heating process took about twenty minutes or so.
More later.


Blogger JT said...

Finally, Nick shows up to help out.... Nice work on the bend. Like you said, if it doesn't work out the first couple of times, there's got to be a better way. Thanks for the trick tip about sand...JT

7:18 PM  
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